Conventionally, as a medium feeding device and an image forming apparatus, for example, there is a printer capable of color printing (hereinafter, this is also referred to as a color printer).
In the conventional color printer, an image forming part that has a plurality of image forming units and the like is provided at a central part of a housing, and a recording sheet feeding part (hereinafter, this is also referred to as a sheet feeding part) that feeds a rectangular recording sheet to the image forming part is provided at a lower part of the case.
In the sheet feeding part, a substantially flat dish-shaped tray (hereinafter, this is also referred to as a sheet feeding tray) for sheet feeding that is capable of loading a plurality of recording sheets in a stacked manner is provided in a manner capable of being pulled out from the housing from a front side of the color printer and being contained in the housing from the front side of the color printer.
A sheet feeding guide part in a projection shape long in a left-right direction is provided at a front end part of the sheet feeding tray. Further, a loading part as a recess part that is long in a front-rear direction and that is surrounded by the sheet feeding guide part, a tray rear plate, left and right tray side plates and a tray bottom plate is provided to the rear of the sheet feeding guide in the sheet feeding tray.
Further, a length of the loading part of the sheet feeding tray in the front-rear direction is selected to be a predetermined length that is longer than a length of a long side of a recording sheet that has a longest long side among recording sheets of a plurality of kinds of sizes such as the A4 size and the B5 size so that any one of the recording sheets of the plurality of kinds of sizes can be loaded in the loading part in a state in which a longitudinal direction of the recording sheets is in parallel to the front-rear direction.
Further, at a rear end part of the tray bottom plate of the sheet feeding tray, a tail guide is provided in a manner moveable in the front-rear direction for defining a loading area of the recording sheet in the loading part with respect to the sheet feeding guide part so that the loading area matches the size of the recording sheet.
Further, near a front side of the loading part of the sheet feeding tray, a placing plate on which one end portions of the recording sheets that are loaded in the loading part is placed is provided in a manner rotatable within a predetermined angle range from a loading position, at which the placing plate is leveled for loading the recording sheets, to a sheet feeding position, at which the placing plate is inclined in a direction parallel to an obliquely forward and upward direction to lift the one end portions of the recording sheets for sheet feeding.
Further, at a predetermined position on an upper side of the sheet feeding tray of the sheet feeding part (that is, on a body of the color printer), a sheet feeding roller is rotatably provided in a state in which a roller shaft of the sheet feeding roller is parallel to the left-right direction.
According to such a configuration of the conventional color printer, when the sheet feeding tray is pulled out from the housing by a user, the placing plate of the sheet feeding tray is rotated to the loading position and is leveled.
Then, by letting the user to suitably adjust a position of the tail guide in the sheet feeding tray, the color printer allows the loading area in the loading part to be defined to match the size of the recording sheets to be loaded.
As a result, the color printer allows a plurality of recording sheets of the same size to be loaded in a stacked state in the loading area that is defined by the user in the loading part of the sheet feeding tray in a manner in which short sides of the recording sheets on a front side are brought into contact with the sheet feeding guide part and are aligned and short sides of the recording sheets on a rear side are brought into contact with the tail guide and are aligned.
Thereafter, when the sheet feeding tray is put in the housing of the color printer by the user, by rotating the placing plate in the sheet feeding tray toward the sheet feeding position side, one end portions of the plurality of the recording sheets that are placed on the placing plate are obliquely lifted.
As a result, among the one end portions of the plurality of the recording sheets that are obliquely lifted in the loading part of the sheet feeding tray of the color printer, an one end portion of a recording sheet that is positioned uppermost is pressed against the sheet feeding roller.
In this way, when a print image is formed, by rotating the sheet feeding roller in the sheet feeding part of the color printer, the plurality of the recording sheets are sequentially fed out one by one from the loading part of the sheet feeding tray toward a front side to be fed to the image forming part (for example, see Japanese Patent Laid-Open Publication No. 2011-195294 (page 4, FIGS. 2 and 3)).
However, in the conventional color printer, a detection lever for detecting presence or absence of loaded recording sheets with respect to the loading part of the sheet feeding tray is provided on an upper side of the sheet feeding tray of the sheet feeding part in a manner rotatable about a rotation shaft in a state in which the rotation shaft that is provided at a base portion of the detection lever is in parallel to the left-right direction.
In this case, although the detection lever rotates so that, for example, a front end part is lowered due to its self weight in a state in which no external force is applied, a rotation regulation part is provided for stopping the rotation at a predetermined rotation regulation position at which the front end part is oriented toward an obliquely rearward and downward side of the rotation shaft.
When the sheet feeding tray is contained in the housing from the front side and when recording sheets of a corresponding size are loaded in the loading area that is defined by the user in the loading part of the sheet feeding tray of the color printer, one end portions of the recording sheets that are lifted by the placing plate are pressed against the front end part of the detection lever from below so that the detection lever is rotated to a position above the rotation regulation position (this is a forward direction).
In this way, when the detection lever is rotated to a position above the rotation regulation position, in response to the rotation, the color printer detects that the recording sheets are loaded in the loading part of the sheet feeding tray.
Further, when an empty sheet feeding tray is erroneously contained in the housing from the front side or when recording sheets are all fed out from the loading part so that the sheet feeding tray contained in the case becomes empty, the color printer rotates the detection lever to the rotation regulation position and stops the rotation.
In this way, when the detection lever rotates to the rotation regulation position, in response to the rotation, the color printer detects that the sheet feeding tray is empty.
When the color printer detects via the detection lever that the sheet feeding tray is empty, the color printer notifies a user about the detection via a display, a speaker, and the like, to prompt the user to load recording sheets in the loading part of the sheet feeding tray.
Conventionally, a movement of the detection lever is sensed by a sensor. When positioned at the rotation regulation position, the sensor detects a part of the detection lever (sense target part), determines that there is no sheet loaded. On the other hand, when the detection lever is lifted by sheets that are loaded, the sense target part rotates in the forward direction from the rotation regulation position together with the detection lever. As the result, the sensor no longer senses the sense target part, determining that sheets are loaded. Herein, it is preferred to design the sense target part to be sensed by the sensor as small as possible in a light of device downsizing. On the other hand, in order to securely detect such a downsized sense target part, the detection lever is required to be located at an identical position at every movement. Considering these matters, conventional detection levers are configured to be allowed to rotate in the forward direction, but not to rotate in the reverse direction.
In the conventional medium feeding device and the image forming apparatus, for example, when the sheet feeding tray is contained in the housing from the front side and when a plurality of recording sheets of a size smaller than a corresponding size are erroneously loaded, in a manner shifted toward the tray rear plate, in the loading area that is defined by the user in the loading part of the sheet feeding tray, one end portions of the plurality of the recording sheets that are lifted by the placing plate are positioned behind the front end part of the detection lever.
As a result, in the medium feeding device and the image forming apparatus, the detection lever cannot be rotated rotation regulation position toward an upper side by the one end portions of the recording sheets that are lifted by the placing plate, so that is detected that recording sheets are not loaded in the sheet feeding tray and the user is notified that the sheet feeding tray is empty.
Then, in the medium feeding device and the image forming apparatus, there is a problem that, when the user is notified that the sheet feeding tray is empty, as described above, and the sheet feeding tray is pulled out from the housing toward the front side by the user, one end portions of the recording sheets in the sheet feeding tray are caught by the detection lever and the recording sheets are damaged. That is because the conventional detection levers are not allowed to rotates in the reverse direction.
The present invention is made by considering the above problem and is intended to propose a medium feeding device and an image forming apparatus that are capable of preventing damage to a medium when a tray is pulled out.